Abstract

The microbiome affects development and activity of the immune system, and may modulate immune therapies, but there is little direct information about this control in vivo. We studied how the microbiome affects regulation of human immune cells in humanized mice. When humanized mice were treated with a cocktail of 4 antibiotics, there was an increase in the frequency of effector T cells in the gut wall, circulating levels of IFN-γ, and appearance of anti-nuclear antibodies. Teplizumab, a non–FcR-binding anti-CD3ε antibody, no longer delayed xenograft rejection. An increase in CD8+ central memory cells and IL-10, markers of efficacy of teplizumab, were not induced. IL-10 levels were only decreased when the mice were treated with all 4 but not individual antibiotics. Antibiotic treatment affected CD11b+CD11c+ cells, which produced less IL-10 and IL-27, and showed increased expression of CD86 and activation of T cells when cocultured with T cells and teplizumab. Soluble products in the pellets appeared to be responsible for the reduced IL-27 expression in DCs. Similar changes in IL-10 induction were seen when human peripheral blood mononuclear cells were cultured with human stool samples. We conclude that changes in the microbiome may impact the efficacy of immunosuppressive medications by altering immune regulatory pathways.

Figure 9

CD11c+ cells were isolated from PBMCs and cultured with pellets as described in the Methods. (A) The expression of CD86 on CD11b+CD11c+ DCs cultured in pellets from antibiotic-treated mice was increased. *P = 0.02 by multiple comparison from ANOVA. (B) Autologous T cells were then added to the cultures with teplizumab and the expression of CD69 was measured on the CD4+ and CD8+ T cells after overnight culture. There was increased expression of CD69 on CD8+ T cells that had been cultured with cells and antibiotic-treated pellets. *P < 0.05, ****P < 0.0001 by 2-way ANOVA with paired comparisons. Abx, antibiotics.